The invention relates to a method for fabricating a master plate and a master plate fabricated thereby having fitting bores disposed at prespecified coordinate intervals.
Clamping plates per se, which are suitable for the accurately fitted and precise clamping and securing of workpieces to be machined or for building machinery and in which bores containing insert sleeves are disposed at precise grid intervals from one another, are known (German Offenlegungsschrift No. 22 32 387; VFW-Focker company publication entitled "VAPA-System"; German Pat. No. 25 57 701; and German Auslegeschrift No. 26 26 155) which are the same as U.S. Pat. Nos. 4,073,215 and 4,310,963, respectively.
In the first two documents mentioned (DE-OS No. 22 32 387 and the VFW-Focker publication), the clamping plates are produced such that bores are first generated in the plate at precise intervals on a grid system, and then insert sleeves having a diameter agreeing with that of the bores are inserted. The bores are created by numerically controlled processing machines of correspondingly high quality and accuracy.
In the remaining publications (German Pat. No. 24 57 701, DE-AS No. 26 26 155), the clamping plates are produced in a completely different manner, however, in the sense they adopt the required high precision of the insert sleeve disposition in the grid system from a master plate, which is responsible for the positioning of the insert sleeves in their bores. In detail, the process of producing such clamping plates for the clamping and securing of workpieces to be machined or for building machinery is such that bores are placed with normal precision in the starting plate--that is, without requiring great precision--with a prespecified dimension for the grid intervals; insert sleeves having a smaller diameter than that of the bores are then inserted, producing an annular interspace all the way around them; finally, the intervals between the various inserted sleeves are determined with the aid of a master plate, serving as a template gauge, which has pins or some sort of positioning elements disposedly spaced apart from one another by highly precise grid interval dimensions. The master plate, which is used only once during fabrication, thus confers its intrinsic accuracy by heredity, as it were, upon the accuracy of a given clamping plate being produced; that is, by introducing a settable plastic material into the interspaces between the diameter of the bore and the outer diameter of the insert sleeve, a fixation of the sleeves in the bores is attained after the plastic material has set. Once the clamping plate is separated from the master plate, the insert sleeves will have taken on the highly precise grid interval dimension and retain it.
In the fabrication of such clamping plates, the fitting or insert sleeves are held in the annular interspace of their receiving bores by means of a plastic material. The accuracy demanded of the master plate is particularly great, because of course tolerances, even if extremely small ones, must be taken into account in making the transfer to a given daughter clamping plate; and these tolerances necessitate an accuracy in the precision positioning of the fixation pins of the master plate which is even higher than the accuracy required and in fact attained for a given clamping plate.